LL-37

LL-37 is a 37-amino-acid peptide that represents the C-terminal active fragment of human cathelicidin antimicrobial protein (hCAP-18). It is the only member of the cathelicidin family found in humans and serves as a critical component of the innate immune system. LL-37 is produced by neutrophils, macrophages, and epithelial cells at barrier surfaces throughout the body.

The peptide possesses direct antimicrobial activity against a broad spectrum of pathogens including gram-positive and gram-negative bacteria, fungi, and enveloped viruses. Its amphipathic alpha-helical structure allows it to insert into and disrupt microbial membranes. Beyond direct antimicrobial action, LL-37 functions as an immune modulator by promoting chemotaxis of immune cells, stimulating angiogenesis, enhancing wound healing, and modulating inflammatory cytokine production.

Research has demonstrated LL-37's effectiveness against antibiotic-resistant bacteria including MRSA, and its ability to disrupt bacterial biofilms. Studies have explored its potential in treating chronic wounds, respiratory infections, and inflammatory conditions. LL-37 deficiency has been associated with increased susceptibility to infections, while its overexpression is linked to inflammatory conditions like rosacea, highlighting its role as a balanced immune regulator. Clinical research continues to investigate its therapeutic potential in chronic infections and wound healing.